Protease inhibitor therapy has greatly increased the lifespan of individuals infected with the human immunodeficiency virus (HIV). Unfortunately, one of the deleterious side effects of protease inhibitor therapy is dyslipidemia which is known to be closely associated with development of atherosclerosis. The development of atherosclerosis is a multifactorial process in which macrophage lipid metabolism plays a central role. In the healthy population, premenopausal women have a lower incidence of atherosclerosis as compared to men. Women on protease inhibitor therapy, however, have similar dyslipidemia as men on protease inhibitor therapy, suggesting that the cardioprotective effects of estrogen are lost. Additionally, preliminary studies in mice show that female mice have significantly fewer atherosclerotic lesions accompanied by a reduced disruption of lipid metabolism in macrophages. Therefore, this proposal will test the hypothesis that the gonadal steroid estrogen modulates the effects of HW protease inhibitors on macrophage lipoprotein metabolism and thus atherosclerotic lesion formation. Aim 1 will determine the ability of 17??estradiol to suppress HIV protease inhibitor-induced macrophage sterol accumulation. We will use the human monocyte/macrophage cell line, THP-1 to define the effects 17??estradiol on the HIV protease inhibitors ritonavir and amprenavir induced alterations of CD36 expression and CD36-dependent function by measuring lipoprotein uptake and cholesterol efflux. Aim 2 will investigate potential mechanisms by which 17??estradiol prevents macrophage dysfunction induced by HW protease inhibitors. An estrogen receptor antagonist will be administered to THP-1 cells to assess the role of estrogen receptors in the regulation of the scavenger receptor CD36 expression and function in the presence of ritonavir and/or amprenavir. We wilt also examine the expression and function of peroxisome proliferating activated receptor gamma (PPAR?) and PPAR? mRNA following estrogen treatment. Aim 3 will determine if 17??estradiol alters the development of atherosclerotic lesions induced by HW protease inhibitors in vivo. We will examine the atherosclerotlc lesion size and lipid metabolism in peritoneal macrophages from intact LDL receptor null mice as well as ovariectomized and estrogen replaced female mice. To determine if estrogen receptors are needed in vivo, LDL receptor null mice will be crossed with estrogen receptor null mice to determine if the estrogen receptors are required for estrogen to prevent atheroscterotic lesions and macrophage dysfunction following HIV protease inhibitor treatment. The data obtained from these studies will be critical to enhancing our understanding of the actions of estrogen in the cardiovascular system as well as estrogen function during HIV infection and protease inhibitor therapy. [unreadable] [unreadable]